Linear-motor conveyor system

ABSTRACT

A tray conveyor in which plastic trays with rows of embedded translators are driven by stators. Washing stations in cleaning zones are provided to automatically clean empty trays in the conveyor&#39;s return path.

BACKGROUND

The invention relates generally to power-driven conveyors and inparticular to tray conveyors driven by linear motors.

Transport systems in which carriers driven by linear synchronous motorsroute individual carriers along various paths in a complex network oftracks are used to convey articles to selected destinations. An exampleof such a transport system is described in U.S. Pat. No. 8,967,051,“Transport System Powered by Short Block Linear Synchronous Motors andSwitching Mechanism,” to Nathanael N. King et al. of Magnemotion, Inc.,Devens, Mass., U.S.A., Mar. 3, 2015. These systems work well, but arenot so easy to clean. The housings of the linear-motor stators presentlarge, flat, closed upper surfaces that collect grease and other foodparticles in food-processing applications. Unless properly cleaned, thesurfaces can become contaminated with bacteria. And hard-to-accessundercut surfaces in the transport system can harbor those bacteria.

SUMMARY

One version of a conveyor system embodying features of the inventioncomprises a plurality of conveyor sections and a plurality of conveyortrays. Each conveyor section comprises a tray guide that extends inlength from a rear end to a front end of the conveyor section and inwidth from a left side to a right side of the conveyor section. At leastone linear stator extends in length through the tray guide between therear end and the front end. The conveyor trays have at least onetranslator that forms a linear motor with the at least one linear statorto drive the conveyor trays along the tray guide in the conveyingdirection. The plurality of conveyor sections are arranged to form acarryway path along which the trays can carry articles and a return pathalong which empty trays return to the carryway path. The conveyor systemcomprises one or more cleaning zones along the return path for cleaningthe trays.

Another version of a conveyor system embodying features of the inventioncomprises a plurality of conveyor sections and a plurality of trays.Each conveyor section has a tray guide that extends in length from arear end to a front end of the conveyor section and in width from a leftside to a right side of the conveyor section. Left-side and right-sidelinear stators extend in length through the tray guide between the rearend and the front end. The left-side linear stator is closer to the leftside, and the right-side linear stator is closer to the right side. Theconveyor trays have translators that form linear motors with theleft-side and right-side linear stators to drive the conveyor traysalong the tray guide in the conveying direction.

Yet another version of a conveyor system comprises a conveyor comprisinga single conveyor segment or a series of conveyor segments and aplurality of conveyor trays. Each conveyor segment comprises a trayguide that extends in length from a rear end to a front end of theconveyor segment and in width from a left side to a right side of theconveyor segment. Left-side and right-side linear stators extend inlength through the tray guide between the rear end and the front end.The left-side linear stator is closer to the left side, and theright-side linear stator is closer to the right side. The conveyor trayshave a translator that forms a linear motor with the left-side andright-side linear stators to drive the conveyor trays along the trayguide in the conveying direction.

In another aspect a conveyor tray embodying features of the inventioncomprises: (a) an article-supporting surface having a front edge, a rearedge, a left edge, and a right edge; (b) a first linear translatordisposed below the article-supporting surface and extending in lengthalong a line intersecting the rear and front edges; (c) a second lineartranslator disposed below the article-supporting surface and extendingin length parallel to the first linear translator between the firstlinear translator and the right edge; (d) a third linear translatordisposed below the article-supporting surface and extending in lengthperpendicular to the first and second linear translators; and (e) afourth linear translator disposed below the article-supporting surfaceand extending in length parallel to the third linear translator betweenthe third linear translator and the rear edge inclusive.

Another version of a conveyor tray comprises: (a) a top surface having afront edge, a rear edge, a left edge, and a right edge defining fourcorners; (b) a left linear translator disposed below the top surface andextending in length along a line parallel to the left edge andintersecting the rear and front edges; (c) a right linear translatordisposed below the top surface and extending in length parallel to theleft linear translator between the left linear translator and the rightedge; (d) a front linear translator disposed below the top surface andextending in length along a line perpendicular to the left and rightlinear translators and intersecting the left and right edges; and (e) arear linear translator disposed below the top surface and extending inlength parallel to the front linear translator between the front lineartranslator and the rear edge.

In another aspect an elevator embodying features of the inventioncomprises first and second vertical sections. Each vertical sectionincludes a vertical left stator rail encapsulating a linear stator and avertical right stator rail parallel to the left stator rail andencapsulating a linear stator. A first carriage rides on the firstvertical conveyor section, and a second carriage rides on the secondvertical conveyor section. Each of the carriages includes: (a) a lefttranslator that extends in length along a left side of the carriagebetween a lower end and an upper end of the carriage and forms a linearmotor with the linear motor encapsulated in the vertical left statorrail; (b) a right translator that extends in length along a right sideof the carriage between the lower end and the upper end and forms alinear motor with the linear motor encapsulated in the vertical rightstator rail; and (c) an upper rail that extends across the upper endfrom the left side to the right side and encapsulates an upper linearstator. The upper rails of the first and second carriages are at thesame level. A first horizontal stator at the top of the first verticalconveyor section and a second horizontal stator at the top of the secondvertical conveyor section form linear motors with the upper linearstators of the first and second carriages.

In another aspect a conveyor embodying features of the inventioncomprises a first elongated enclosure having open ends and a conveyingsurface that extends along a length of the first elongated enclosure. Aleft-side linear stator extends in length along the left side of theconveying surface, and a right-side linear stator extends in lengthalong the right side of the conveying surface. A plurality of conveyortrays supported on the conveying surface, the conveyor trays havetranslators that form linear motors with the left-side and right-sidestators to drive the conveyor trays through the first elongatedenclosure.

Another version of a conveyor tray comprises a tray body having anarticle-supporting surface, a front edge, a rear edge, a left edge, anda right edge. A first linear translator is disposed below thearticle-supporting surface and extends in length along a lineintersecting the rear and front edges. A second linear translator isdisposed below the article-supporting surface and extends in lengthparallel to the first linear translator between the first lineartranslator and the right edge. A left skirt extending downward from theleft edge, and a right skirt extends downward from the right edge. Thefirst linear translator is disposed in the left skirt and the secondlinear translator is disposed in the right skirt.

A carriage for a tray conveyor embodying features of the inventioncomprises a tray guide extending in length from a rear end to a frontend of the carriage and in width from a left side to a right side of thecarriage. Left and right linear stators extend in length through thetray guide between the rear end and the front end. The left linearstator is closer to the left side, and the right linear stator is closerto the right side. A rear translator is disposed at the rear end of thecarriage, and a front translator is disposed at the front end of thecarriage.

A carriage assembly embodying features of the invention comprises acarriage and a motor rotating the carriage through a predeterminedangle. The carriage includes a first linear stator that extends inlength along one side of the carriage and a second linear stator thatextends in length along the opposite side of the carriage.

A conveyor embodying features of the invention comprises a plurality oftrays and a conveyor section that includes a linear-motor stator. Eachtray includes a linear-motor translator that forms a linear motor withthe linear-motor stator to convey the tray along the conveyor sectionand indicia indicating a family of which the tray is a member. A sensorsensing the indicia and sends a sensor signal to a controller. Theconveyor section is assigned to convey trays that belong to apredetermined family. The controller determines the family of the trayfrom the sensor signal and stops the conveyance of the tray on theconveyor if the family of the tray does not match the predeterminedfamily.

In another aspect a method embodying features of the invention foroperating a conveyor comprises: (a) assigning each of a plurality ofconveyor trays to one of a plurality of families by indicia indicatingthe assigned family; (b) assigning a predetermined family of conveyortrays to a conveyor; (c) identifying the assigned family of eachconveyor tray on the conveyor; (d) identifying conveyor trays whosefamily does not match the predetermined family assigned to the conveyor;(e) removing the conveyor trays whose family does not match thepredetermined family assigned to the conveyor from the conveyor; and (f)conveying the conveyor trays whose family matches the predeterminedfamily along the conveyor through a process.

In another aspect one version of a rail scrubber embodying features ofthe invention comprises front and rear wheels riding along left andright conveyor rails of a conveyor and left and right scrubbing wheelshaving brushes engaging the left and right conveyor rails. Nozzlespositioned at the left and right conveyor rails to spray fluid from afluid tank onto the left and right conveyor rails. A drive system drivesthe rail scrubber along the left and right conveyor rails.

Another version of a scrubber comprises front and rear wheels ridingalong a top surface of a conveyor, left and right scrubbing wheelshaving brushes engaging the top surface of the conveyor, nozzlespositioned to spray fluid from a fluid tank onto the top surface of theconveyor, and a drive system driving the scrubber along the top surfaceof the conveyor.

Another version of a conveyor comprises a tray and a conveyor sectionsupporting the tray. The tray includes a tray body having an uppersurface and an opposite underside, a plurality of rollers in the traybody, and a linear translator at the underside extending in length alongthe length of the tray. The conveyor section includes a linear drivestator that extends in length along the conveyor section adjacent thelinear translator and forms a linear motor with the translator to propelthe tray along the conveyor. A tray-roller actuator coacts with theplurality of rollers to rotate the rollers as they pass by.

In another aspect a conveyor tray comprises a tray body having an uppersurface and an opposite underside, a plurality of rollers that extendthrough the thickness of the tray body past the upper surface and theunderside, and a linear translator at the underside that extends inlength along the length of the tray.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a conveyor segment of a linear-motorconveyor system embodying features of the invention;

FIG. 2 is a partly cutaway enlarged view of a portion of the side railof a conveyor segment as in FIG. 1;

FIG. 3 is a partly cutaway isometric view of a conveyor segment as inFIG. 1 showing embedded electronic circuits and wiring;

FIG. 4 is a block diagram of the electronic circuits of FIG. 3;

FIG. 5 is an isometric view of confronting end portions of two adjacentconveyor segments as in FIG. 1;

FIG. 6 is an isometric view of two joined conveyor segments as in FIG.1;

FIG. 7 is an isometric view of a conveyor tray usable with the conveyorsegment of FIG. 1;

FIG. 8 is an isometric view of a portion of a conveyor tray as in FIG. 7with a Halbach magnet array;

FIG. 9 is an isometric view of a carriage usable with a conveyor segmentas in FIG. 1;

FIG. 10 is an enlarged isometric view of a corner portion of a carriageas in FIG. 9 showing vertical and horizontal translators in a partlyopen housing;

FIG. 11 is a block diagram of the electrical circuit in the carriage ofFIG. 9;

FIGS. 12A-12D are isometric views of a three-dimensional tray sorterconstructed of conveyor segments as in FIG. 1;

FIG. 13 is an isometric view of an accumulator constructed of conveyorsegments as in FIG. 1;

FIGS. 14A-14C are isometric views of a merge conveyor constructed ofconveyor segments as in FIG. 1;

FIGS. 15A-15C are isometric views of a multi-tray sorter constructed ofconveyor segments as in FIG. 1;

FIG. 16 is an isometric view of a conveyor tray usable in a multi-traysorter as in FIGS. 15A-15C;

FIG. 17 is an isometric view of an elevator usable with the conveyorsegments of FIG. 1;

FIGS. 18A and 18B are isometric views of the elevator of FIG. 17 inlowered and raised positions;

FIG. 19 is an isometric view of a square spiral conveyor constructed ofconveyor segments as in FIG. 1 and elevators as in FIG. 17;

FIGS. 20A-20C are isometric views of an elevator system constructed ofconveyor segments as in FIG. 1 with separate up and down pathsdelivering trays into an overhead pipe;

FIGS. 21A-21C are axonometric views of a cover tray, a conveyor tray,and a cover tray covering a conveyor tray for use in a conveyor systemembodying features of the invention;

FIGS. 22A-22D are isometric views of a conveyor system using conveyorsegments as in FIG. 1 to put a cover over a conveyor tray;

FIGS. 23A-23C are isometric views of the conveyor system of FIGS.22A-22D illustrating the removal of a tray cover;

FIG. 24 is an isometric view of a diverter usable with conveyor segmentsas in FIG. 1;

FIG. 25 is an enlarged transparent view of a portion of the diverter ofFIG. 24 illustrating a curved stator;

FIGS. 26A-26D are isometric views of a portion of a conveyor including adiverter as in FIG. 24;

FIG. 27 is an enlarged isometric view of the crossing portion of railsin the diverter conveyor of FIGS. 26A-26D;

FIG. 28 is an isometric view of a conveyor using curved conveyorsegments as in FIG. 1 in a return path;

FIGS. 29A and 29B are top and bottom isometric views of another versionof a conveyor tray for use in a conveyor system embodying features ofthe invention;

FIG. 30 is an isometric view of a portion of a conveyor systemconstructed of conveyor segments compatible with the conveyor trays ofFIGS. 29A and 29B;

FIG. 31 is an isometric view, partly in phantom, of a two-axistranslator in the carriage of an elevator system as in FIGS. 20A-20D;and

FIGS. 32A and 32B are side elevation views of a fail-safe braking systemattached to the translator of FIG. 31 in non-braking and brakingpositions.

FIG. 33 is an isometric view, partly cut away, of a portion of anotherversion of a conveyor segment for moving a conveyor tray as in FIGS. 29Aand 29B;

FIG. 34 is an isometric view of the conveyor segment of FIG. 33;

FIG. 35 is an isometric view of a conveyor segment as in FIG. 33 withair-bearing levitation instead of magnetic levitation;

FIG. 36 is an enlarged exploded view of two abutting conveyor segmentsas in FIG. 34;

FIG. 37 is an isometric view of a portion of a conveyor sectionconstructed of conveyor segments as in FIG. 34;

FIG. 38 is an isometric view of a conveyor, partly in phantom,constructed of conveyor segments as in FIG. 34 and an x-y conveyorsection;

FIG. 39 is an isometric view of a conveyor switch using an x-y conveyorsection as in FIG. 38;

FIG. 40 is an isometric view of a merge conveyor using an x-y section asin FIG. 38;

FIG. 41 is an isometric view, partly cut away, of a carriage usable witha conveyor tray as in FIGS. 29A-29B;

FIG. 42 is an isometric view of a portion of a bi-level conveyor systemusing a carriage as in FIG. 41;

FIG. 43 is an isometric view of a linear-motor-driven diverting conveyorusing a conveyor tray having oblique article-supporting rollers todivert articles off one side of the conveyor;

FIG. 44 is an isometric view of the conveyor of FIG. 43 divertingarticles off the opposite side;

FIG. 45 is an isometric view of a diverting conveyor as in FIG. 43, butwith stacked article-supporting roller sets, and FIG. 45A is an enlargedview of one of the stacked roller sets;

FIG. 46 is an isometric view of a bilateral diverting conveyor in whichthe conveyor tray has rollers selectively rotatable on axes parallel tothe main conveying direction, and FIG. 46A is an enlarged view of aportion of the conveyor;

FIG. 47 is an isometric view of a rail scrubber with its cover removedused for cleaning the rails of a conveyor segment as in FIG. 1;

FIG. 48 is an isometric view of the rail scrubber of FIG. 47 with thecover in place;

FIG. 49 is an isometric view of a conveyor system constructed ofsections of conveyor segments as in FIG. 1 configured for preventingcross contamination of products through the use of dedicated trays;

FIG. 50 is an isometric view of a rail scrubber as in FIG. 48 cleaning aconveyor section as in FIG. 49;

FIGS. 51A and 51B are isometric views of a discharge end of a pipeconveyor and its same-level return embodying features of the inventionincluding a tilt carriage shown in horizontal and tilted positions;

FIGS. 52A-C are isometric views of a discharge end of a pipe conveyorand a lower-level return embodying features of the invention withanother version of a tilt carriage;

FIG. 53 is an isometric drawing of a conveyor section with lower returnand a rotary reversing carriage at each end to form an endless loopembodying features of the invention;

FIG. 54 is an isometric view of an underside corner of a carriage trayas in FIG. 7 with a magnetic strip interacting with a conductive stripin a conveyor rail as in FIG. 3;

FIG. 55 is an isometric view of a conveyor segment as in FIG. 1 with alinear-motor stator driving rollers in a conveyor tray;

FIG. 56 is an isometric view of another version of a one-level divertersection usable in various conveyor, such as a merge conveyor as in FIGS.14A-14C;

FIG. 57 is an isometric view of a dual-rail elevator using a pair ofcarriages as in FIG. 56 to form a tray platform;

FIG. 58 is an isometric view of a racetrack portion of a conveyorsection made of conveyor segments as in FIG. 1, but curved;

FIG. 59 is an isometric view of a scrubber for cleaning conveyorsegments as in FIG. 34; and

FIG. 60 is an isometric view of an endless conveyor made of conveyorsegments as in FIG. 34 with elevator carriages at each end.

DETAILED DESCRIPTION

A conveyor segment for constructing a cleanable conveyor systemembodying features of the invention is shown in FIG. 1. The conveyorsegment 100 comprises left and right side rails 102, 104 extending inlength in a conveying direction 106. The two side rails are supported ina minimal conveyor frame comprising legs 108 and connecting structure inthe form of cross beams 110 maintaining the two side rails 102, 104parallel to each other. The entire conveyor frame is made of a plasticmaterial, but could be made of other materials. Top surfaces 112 of theside rails 102, 104 and top surfaces 114 of the cross beams 110 areconvexly curved, or rounded, to minimize the buildup of grease andcontaminants.

As shown in FIG. 2, a three-phase linear-motor stator 116 is embedded inthe right side rail 104. A similar stator is embedded in the left siderail. The stator 116 comprises a series of poles separated by slots in alinear core. Three-phase windings in the slots complete the stator. Thecore can be ironless to avoid the frictional effects of remanentmagnetism when not energized. When energized, the stator 116 produces amagnetic flux wave that travels along the side rail 104 in or oppositeto the conveying direction 106 shown. The magnetic flux wave is directedhorizontally outward from the outer wall 118 of the side rail 104 inthis example. Also embedded in the side rail 104 are sensors 120 atspaced apart sensor positions along the side rail's length. Each sensor120 is used to detect the presence of a tray on the side rails at thesensor position.

The stators 116 and the sensors 120 are powered and controlled byelectronic and power circuits 122 embedded in the cross beams 110 overwires 124 embedded in the conveyor frame and the side rails 102, 104 asshown in FIG. 3. Power, control, and data wires 126 connecting theelectronics module 122 to a source of power and a system controller areembedded in the legs 108 of the conveyor frame. Because the wires,electronics, stators, and sensors are all encapsulated in the conveyorframe and side rails, the conveyor segment provides no flat surfaces ornooks and crannies that can collect and harbor contaminants. So theconveyor segment is easy to clean.

A block diagram of the electronics module and the stator drive is shownin FIG. 4. The stator 116 comprises a linear series of three sets ofcoils 130A, 130B, 130C—one set for each of the three phases—alternatelyarranged along the length of the side rail. Each set of coils 130A,130B, 130C is driven by an amplifier 132A, 132B, 132C. The phasingsequence and frequency of the stator 116 are controlled through a statordrive control 134, which sends coil control signals 136A, 136B, 136C tothe amplifiers 132A, 132B, 132C. The stator drive control 134 includes acomputer in communication with a remote system computer 140, which alsocommunicates with the stator drive controls in other conveyor segments.The stator drive control 134 receives commands from and sends data tothe system computer 140 wirelessly or over a hard-wired connection 142.The sensors 120 send sensor signals 146 indicating the position of aconveyor tray over a sensor bus to the stator drive control 134, whichuses those signals to determine when to energize and de-energize thestator 116. All those components, except for the remote system computer140, are encapsulated in the conveyor frame as in FIG. 3. The magneticflux wave produced by the stator in the rail causes a conveyor tray withan embedded permanent-magnet array 148 to advance along the rail in theconveying direction 106.

FIG. 5 illustrates how two adjacent conveyor segments 100, 100′ aremaintained with their left and right side rails 102, 104 aligned to formcontinuous rails. An alignment magnet 150 is embedded in the end of anappendage 152 at the bottom of each side rail 102, 104. A similar magnet154 is embedded in a similar appendage 156 at the confronting end of theside rail of the adjacent conveyor segment 100′. The magnets 150, 154are arranged with their opposite poles facing each other so that theyattract. The attraction of the magnets keeps the confronting rails inalignment. Instead of having magnets in both confronting side-rail ends,one end could have a piece of ferrous material that would be attractedby the magnet in the adjacent conveyor segment to maintain alignment.

A short conveyor section constructed of two conveyor segments 100, 100′is shown in FIG. 6 supporting a series of conveyor trays 160 on the tops112 of the side rails 102, 104, which serve as a tray guide. The trays160 are not connected to each other and are independently movable in oropposite to the conveying direction 106 by the stators embedded in theside rails 102, 104. The trays 160 can be simply lifted from theconveyor segment for cleaning, maintenance, or other removal needs. Andthe trays can be replaced on the conveyor segment just as easily. Asshown in FIG. 7, each tray 160 is shown as a rectangular tray body 161with a rear edge 162, a front edge 164, a left edge 166, and a rightedge 168. The tray 160 has an upper article-supporting surface 170extending to the edges 162, 164, 166, 168. Skirts 172, 174 extenddownward from the left and right edges 166, 168. Embedded in each skirt172, 174 is an array of permanent magnets 176 extending in length alongthe skirt between the rear and front edges 162, 164. The magnet arraysare arranged with their magnetic fields directed generally parallel tothe article-supporting surface 170 to maximize the magnetic couplingwith the traveling magnetic wave produced by the stators in the siderails of the conveyor segments. The skirts 172, 174 overlap the conveyorside rails and help keep the trays 160 laterally in place. At least theskirts 172, 174 are made of a non-magnetic material, such as plastic.And the upper article-supporting surface 170 can be continuous orforaminous, flat or curved, and smooth or textured with nubs, cones,diamonds, or other patterns. Furthermore, the conveyor tray could haveleft, right, front, and rear sides standing up from the left, right,front, and rear edges for use as, for example, a baking pan. Thearticle-supporting surface 170 could extend beyond the front, rear,left, and right edges of the main tray body.

Straight conveyor segments 100, 100′ as in FIG. 6 can be joined tocurved conveyor segments 900 as in FIG. 58 to form a banked racetrackconveyor section 906. The side rails 902, 904 of the curved segments 900are curved out of coplanarity with the straight segments to form thebanked racetrack section 906. Articles 908 carried on the conveyor trays160 are diverted off the trays 160 and over the lower side rail 902 uponentering the banked racetrack section 906. In this way the racetrackserves as a tilt conveyor to allow conveyed products to drop from thetrays in the banked section 906. The banked racetrack section 906 alsopermits the construction an endless track without a lower returnwayalong its entire circuit. And the trays 160 are shown routed through awashing station including a cleaning zone containing an automaticwashing enclosure 909 like that used in car washes along a returnsection 907 downstream of the banked section 906. Washing the trays 160in the automatic washing enclosure 909 in the return 907 reduces oreliminates the manual washing of the trays and, thus, increasesproductivity and ensures consistent tray hygiene.

For even better magnetic coupling, the permanent-magnet arrays can bearranged as Halbach arrays 178 with the magnets arranged in alternatingpolarities as shown in FIG. 8. Each magnet array, whether Halbach ornot, forms the secondary of a magnetic circuit whose primary is thestator in a side rail. When the secondaries are permanent magnet arrays,they form a linear synchronous motor with the stators. The magnet arrayin the tray could be replaced with electrically conductive material inwhich the magnetic flux wave produced by the stator induces eddycurrents. The eddy currents produce a secondary magnetic field thatinteracts with the stator's primary magnetic field, i.e., the travelingmagnetic flux wave, to generate a propulsive force to move the trayalong the rail. When electrically conductive material is used instead ofmagnets in the tray, the electrically conductive material forms a linearinduction motor with the stator. As another alternative, the tray couldhave a platen including a linear array of pole faces with three-phasewindings with a different pole pitch from that of the three-phase statorpoles on a stator platen to form a linear reluctance motor. Whetherlinear synchronous, induction, or reluctance motors are formed, thesecondaries in the trays are referred to in this description and in theclaims as translators—analogous to rotors in a standard rotating motor.And, as shown in FIG. 54, the trays could include magnetic strips 700extending along their undersides in the joints 702 between the skirts703 and the bottom of the article-supporting surface 704. As the traysadvance along a conveyor segment 706, the magnetic fields of themagnetic strips 700 induce currents in electrically conductive strips708 embedded in and extending the length of stator rails 710. Theinduced currents create induced magnetic fields that interact with themagnetic fields of the magnets to produce a levitation force actingupward and outward on the trays for low-friction, levitated travel.

A carriage for carrying a tray in a horizontal or a vertical directionor for propelling a tray along its rails is shown in FIG. 9. Thecarriage 180 comprises a left rail 182 and a right rail 184 connectedand maintained in parallel by a pair of connecting members 186. The topsof the left and right carriage rails 182, 184 form a two-rail carriagetray guide for the trays. Like the rails in the conveyor segments, theleft rail 182 encapsulates a left linear stator, and the right rail 184encapsulates a right linear stator. A rear translator at a rear end 188of the carriage 180 comprises a left rear translator in a left rearhousing 190 suspended below and outward of the left rail 182 and a rightrear housing 192 suspended below and outward of the right rail 184. In asimilar way a front translator at a front end 189 of the carriage 180comprises left and right front translators in left and right fronthousings 194, 196. As shown in FIG. 10, each translator includes one ortwo three-phase windings. In this example the right rear housing 192,shown open to reveal the translators suspended from the right rail 184at the rear end 188, has a vertical translator 200 and a horizontaltranslator 202. The vertical translator 200 has a horizontal magneticaxis 204, and the horizontal translator 202 has a vertical magnetic axis206. The translators in the corner housings 190, 192, 194, 196, besidescoacting with conveyor-frame stators to propel the carriage along atrack, couple power to the stators in the left and right rails 182, 184.The rail stators, when energized, propel trays along and off the rails182, 184. So the translators are electrically connected to the railstators. The carriage could also encapsulate one or more weight sensors207 in the rails 182, 184 or in the corner translator housings 190, 192,194, 196 to weigh the trays and their contents.

FIG. 11 is a block diagram of the circuit embedded in the carriageframe. The carriage-rail stator drive system including the three-phasestator coils 130, the coil-drive amplifiers 132, the carriage drivecontrol 134, and the position sensors 120 is schematically the same asfor the conveyor segments described with respect to FIG. 4. The statordrive-system components are distributed between the rails and thetranslator housings within the carriage frame. The output 199 of thethree-phase horizontal and vertical translator windings 201 provideselectrical power to the drive control 134, amplifiers 132, and railstators 130 to drive the conveyor-tray translators 148 and to theposition sensors 120 and the weight sensors 207. The translator windings201 receive power inductively from a conveyor-frame stator 203.Power-line communication, in which data on a high-frequency carrier issuperposed on the ac power, is used to communicate data and controlsignals between the carriage drive control 134 and the system computer.The position sensors 120 and the weight sensors 207 send sensor signalsto the carriage drive control 134. A power and communication system 205includes: (a) a filter section to separate the communication signalsfrom the ac power; (b) a rectifier to convert the ac power into dc; (c)a voltage regulator regulating the dc voltage to power the carriagedrive control 134; (d) a decoder to decode received communicationsignals; and (e) a modulator and line driver to transmit outgoing datamessages including tray position and weight data over the translatorwindings 199. The stator drive control 134 processes the decodedincoming messages received from the power and communication system 205and sends data messages to the power and communication system fortransmission over the power system. The carriage translator 201 forms aswitched-reluctance linear motor with the conveyor-frame stator 203 tomove the carriage. When the carriage is stopped, the power from theconveyor-frame stator 203 is used to drive conveyor trays along thecarriage rails.

FIGS. 12A-12D describe one example of a conveyor system using acarriage. The conveyor has four conveyor sections: a first lower section210; a second lower section 212 in line with the first lower section210; a third lower section 214 parallel to and laterally offset from thefirst conveyor section 210; and a fourth upper section 216 horizontallyand vertically offset from the first conveyor section 210. The fourconveyor sections 210, 212, 214, 216 are separated from each otheracross gaps forming a main space 218. A gantry is disposed in the space218. The gantry has two parallel horizontal guide tracks 222, 224 andthree pairs of parallel vertical guide tracks 226, 228, 230. To simplifythe drawing the gantry frame supporting the guide tracks is not shown.The translator housings 190, 192, 194, 196 ride in the guide tracks 222,224, 226, 228, 230. Upper lips 231 along the sides of the guide tracksretain the translator housings in the tracks. Each of the guide tracksincludes a linear stator (not shown) extending along the length of theguide track selectively propagating a magnetic flux wave along the trackto propel the carriages' translators. A carriage 180 with a conveyortray 160 atop it is shown in FIG. 12A in a position in which the tray160 can be passed along the carriage rail from the first lower conveyorsection 210 to the inline second lower conveyor section 212. The leftand right rails of the carriage in that position are effectivelycontinuous with the left and right side rails of the first and secondconveyor sections 210, 212. If the tray 160 is selected for anotherdestination, the carriage 180 is propelled along the horizontal guidetracks 222, 224 to a position in which the rails are aligned with thethird lower conveyor section 214 as shown in FIGS. 12B and 12C. Thestators in the carriage may then be energized to propel the tray 160 offand onto the third conveyor section as shown in FIG. 12C. If thescheduled destination is the upper conveyor section 216, the carriage180 is raised by the stators in the vertical guide tracks 226, 228 tothe level of the upper conveyor section, as shown in FIG. 12D. Thecarriage's stator rails are then energized to propel the tray 160 offthe carriage 180 and onto the upper conveyor section 216.

A more complex conveyor system is shown in FIG. 13 in which two rows ofgantries 220, 221 are used to move a carriage 180 with trays 160horizontally and vertically along guide tracks from an infeed conveyorsection 230 onto or off parallel conveyor sections 232 arranged inmultiple horizontally offset rows of vertically stacked conveyorsections to accumulate trays with articles for later processing. Trayscarrying articles scheduled for processing are passed directly acrossthe carriage 180 in its home position shown in FIG. 13 from the infeedconveyor section 230 onto a discharge conveyor section 234. When traysin the accumulator section 232 are scheduled for processing, they aremoved to a position at the gantries 221 and onto a carriage 180, whichis then moved along the guide tracks to the home position so the traycan be propelled off the carriage and onto the discharge conveyorsection 234. Although only a single carriage 180 is shown in thegantries 220, 221 in FIG. 13, more than one carriage can be used.

FIGS. 14A-14C depict the operation of a merge conveyor constructed ofthree infeed conveyor sections 236, 238, 240 with dual stator rails 242,244 as in the conveyor section of FIG. 1. The three infeed sections 236,238, 240 are shown side by side in parallel. A first pair 246 ofhorizontal guide tracks extends perpendicular to the conveying direction106 at the common ends of the left and center infeed conveyor sections236, 238. The first pair 246 of guide tracks bridges those two conveyorsand forms a first diverter section. A first carriage 248 (FIG. 14C)rides on the first pair 246 of tracks to move trays 160 horizontally toa discharge conveyor section 250 in line with the center infeed conveyor238 across a space. The right infeed conveyor section 240 extends pastthe ends of the other two infeed sections 236, 238 to an end 252laterally across from the front end of the first carriage 248. A secondpair 247 of guide tracks parallel to the first pair 246 bridges thespace between the right infeed conveyor section 240 and the dischargeconveyor section 250. The second pair 247 of guide tracks form a seconddiverter section to drive a second carriage 254. The sequence ofoperations required to merge Tray 1, Tray 2, and Tray 3 onto thedischarge conveyor section 250 is as follows:

-   -   1. transport Tray 1 on the right infeed conveyor section 240        onto the second carriage 254 as in FIG. 14A;    -   2. transport Tray 2 on the left infeed conveyor section 236 onto        the first carriage 248 as in FIG. 14A;    -   3. move the second carriage 254 and Tray 1 laterally along the        second set 247 of guide tracks until the carriage is aligned        with the discharge conveyor section 250;    -   4. move the first carriage 248 and Tray 2 laterally along the        first set 246 of guide tracks until the carriage is in line with        the discharge conveyor section 250;    -   5. with the two carriages 248, 254 both in line with the center        infeed conveyor section 238 and the discharge conveyor section        250, energize all those rails to propel Tray 1, Tray 2, and Tray        3 onto the discharge conveyor section as in FIG. 14B;    -   6. return the carriages 248, 254 to their positions in line with        the left and right infeed conveyors 236, 240 as required to        collect the next set of trays to be merged onto the discharge        conveyor section 250 as in FIG. 14C.        In this one-level version no vertical elevation is required, and        the translators 256 in a connecting member 258 joining the rails        of the carriages 248, 254 require only horizontal translators.        The same configuration of conveyor sections can be used as a        1-to-3 switch by reversing the conveying direction 106. In that        case, the discharge conveyor section 250 would operate as an        infeed conveyor section, and the three infeed conveyor sections        236, 238, 240 would be discharge conveyors, with the guide        tracks 246, 247 and carriages 248, 254 as the switches.

Another version of a diverter section 818 is shown in FIG. 56. Acarriage 820 has rear and front skirts 822, 824 depending from acarriage body 826. The skirts 822, 824 have built-in translators, suchas permanent-magnet arrays as in the conveyor trays. The divertersection 818 has stator rails 828, 830 like those in the conveyorsegments of FIG. 1. The carriage 820 moves along the tracks defined bythe rails 828, 830 in a translation direction 832. Cross pieces 834joining the diverter's stator rails 828, 830 house coils that energizethe stators in carriage rails 836, 838 extending upward from left andright sides of the carriage body 826. When the carriage rails 836, 838are aligned with rails 840, 842 of discharge or infeed conveyorsections, the carriage-rail stators are energized to induct trays 844like the tray of FIG. 7 onto or to propel them off the carriage.

FIG. 57 shows a dual-rail elevator 850 using two carriages 852, 854 toform an elevator platform for a conveyor tray 856. The carriages 852,854 are similar to the carriage 720 shown in FIG. 56. The elevator 850comprises two upgoing vertical conveyor sections 858, 860 each with leftand right stator rails 862, 864. At the top of each upgoing conveyorsection 858, 860 is a shuttle conveyor segment 863 with stator rails 865aligned with the left and right stator rails 862, 864 in a firstposition. Each shuttle 863 translates laterally outward as indicated byarrows 857 with one of the carriages 852, 854 from an associated upgoingconveyor section 858, 860 to one of two downgoing conveyor sections 869,871 with left and right stator rails 873, 875. When the shuttles are ina second position with their rails 865 aligned with the downgoing rails873, 875, the carriages 852, 854 are advanced onto the downgoing rails873, 875 for their trips back to the bottom of the elevator 850. Thenthe upper shuttles 863 return inward to their first positions. Identicallower shuttles 877 are disposed at the bottom of the elevator 850 tocarry the carriages 852, 854 from the outer downgoing rails 873, 875 tothe inner upgoing rails 862, 864. In this up-down elevator 850, multiplepairs of carriages can run simultaneously. (The operation of theshuttles 863, 877 is also described in reference to elevator carriagesshown in FIGS. 22A-22D, which operate identically in moving verticallyinstead of horizontally.) The upgoing conveyor sections 858, 860 arearranged in parallel, facing each other in a conveyor frame 866. Thecarriages 852, 854 have left and right skirts 868, 870 with translators,such as an array of permanent magnets, that form linear motors with thelinear stators in the vertical stator rails 862, 864. The linear motorsdrive the carriages 852, 854 up the upgoing elevator rails 862, 864.Each carriage 852, 854 has an upper stator rail 872 at its upper end.The stator in the carriages' upper rails 872 form linear motors withtranslators in the tray's skirts 874 to induct the tray 856 onto orpropel it off the elevator 850. The two carriages 852, 854 are driven upand down parallel to each other with their upper rails even to form alevel platform for the tray 856. At the bottom of the elevator 850, theupper carriage rails 872 are aligned with rails 876 of a lower conveyorsection 878. Coils in horizontal cross pieces 880 in the lower shuttles877 energize the stators in the carriage's upper rails 872. Theenergized carriage stators induct trays 856 onto or propel them off thecarriage platform. Coils are also disposed in upper cross pieces 882 inthe upper shuttles 863 at the top of the elevator 850 to similarly feedtrays 856 to or receive trays from an upper conveyor section 884. Incase power to the elevator 850 is interrupted, each carriage 852, 854has a brake (not shown, but described later) that engages to prevent thecarriage from falling.

A multi-tray sorter is shown in FIGS. 15A-15C. A pair of side-by-sideinfeed conveyor sections 260, 262 transport a group of four conveyortrays 264 in a conveying direction 106. The infeed conveyor sections260, 262 are spaced apart from four discharge conveyor sections 266,267, 268, 269 across a space 270. Two horizontal guide tracks 272 arepositioned in the space 270 perpendicular to the conveying direction106. The guide tracks 272 support and drive a pair of carriages 274, 276along the tracks. The carriages 274, 276 receive the trays 264 from theinfeed conveyor sections 260, 262 and move them laterally to theirdestination infeed conveyor section as shown in FIGS. 15B and 15C. Thecarriage rails are then energized to propel the trays 264 onto thedestination outfeed conveyor section. Two carriages 274, 276 areused—one for each infeed conveyor section 260, 262. Running a multi-traysorter in reverse changes the conveyor's operation to that of a combinerjoining individual groups of trays into a larger multi-tray.

To ensure that the trays 264 remain together as a group on the infeedconveyor sections, clamping magnets are positioned on the trays as shownin FIG. 16. Each conveyor tray 264 has a rear clamping magnet 280 and afront clamping magnet 282. The front and rear clamping magnets attractthe rear and front clamping magnets of leading and trailing trays on thesame infeed conveyor section. For example, the rear clamping magnet ofTray 1 in FIG. 15A attracts the front clamping magnet of Tray 2 to keepthe trays together on the left infeed conveyor section 260. Either thefront clamping magnet 282 or the rear clamping magnet 280 could bereplaced by a ferrous material that would be attracted by the clampingmagnet of the leading or trailing tray. As shown in FIG. 16, the magnetsare polarized to exert a high magnetic clamp force along a polar axis ina direction 284 perpendicular to the front and rear edges 286, 287 ofthe trays 264 and a lower magnetic shear force in a direction parallelto the front and rear edges. That polarization holds consecutive traystogether on each infeed conveyor, but allows them to be separated easilyby the carriages 274, 276 (FIG. 15) for sorting as in FIGS. 15B and 15C.To keep laterally adjacent conveyor trays in each group together, suchas Tray 1 and Tray 3 or Tray 2 and Tray 4 in FIG. 15A, the conveyortrays 264 have one or more left and right clamping magnets 288 at theleft and right edges 290, 292 of the conveyor trays. The left and rightclamping magnets 288 are polarized to exert a high shear force along apolar axis in a direction 294 parallel to the left and right edges 290,292 and a lower clamp force perpendicular to the left and right edges.In this way the laterally adjacent trays are held together side by sidein the infeed conveyor and easily separated laterally by the carriagesfor sorting. Like the front and rear clamping magnets, one or the otherof the left and right clamping magnets can be replaced by a ferrousmaterial to be attracted to the clamping magnet.

A right-angle elevator section usable with conveyor segments as in FIG.1 is shown in FIG. 17. The elevator 300, shown in a raised position,comprises a carriage 301 having left and right stator rails 302, 304maintained in parallel by cross members 306. Vertical translators 308depend from the left and right rails 302, 304 at rear and front ends310, 312. The translators are electrically connected to stators embeddedin the elevator rails 302, 304. The elevator carriage 301 is supportedon a frame 314 that has vertical guide tracks 316 backed by an embeddedvertical linear stator at each corner. The stators backing the verticalguide tracks 316 form linear motors with the translators 308 that raiseand lower the elevator carriage 301. The elevator frame 314 also has apair of parallel stator rails 316, 318 that are perpendicular to theelevator carriage rails 302, 304. When the carriage 301 is in its lowerposition, the carriage rails 302, 304 sit at a level lower than thelevel of the frame rails 316, 318 to provide clearance for the conveyortrays as they enter the elevator 300.

The operation of the right-angle elevator is shown in FIGS. 18A and 18B.A conveyor tray 320 is shown advancing along an infeed conveyor section322 in FIG. 18A toward a right-angle elevator section 300. The rails ofthe infeed conveyor section 322 are aligned with the elevator framerails 316, 318 so that the tray 320 can be transferred onto the loweredelevator carriage 301. Once the tray 320 is on the lowered elevatorcarriage, the elevator 300 lifts the carriage 301 and tray 320 to theupper position shown in FIG. 18B. Besides having left and right skirts324, 326 with translators, the tray 320 has rear and front skirts 328,330 with translators. When the tray 320 is lifted by the elevator 300off the frame rails 316, 318, it is supported by the carriage rails 302,304. The skirts 324, 326, 328, 330 do not extend all the way to thecorners of the trays 320. Slits 332 are formed in the skirts 324, 326,328, 330 at each of the four corners of the trays 320. The slits 332provide passages for the elevator rails so that the trays 320 can betransferred onto the elevator 300 and off at a right angle onto adischarge conveyor section 334.

FIG. 19 shows a rectangular spiral conveyor constructed of conveyorsegments as in FIG. 1 and right-angle elevators as in FIG. 17 at thecorners. The spiral conveyor 340 is constructed of conveyor sections 342arranged to form one tier of a four-sided stepped spiral of consecutiveconveyor sections vertically offset from each other. An elevator section300 at each corner of the spiral conveyor raises or lowers trays 320from one vertical level to the next. Multiple tiers can be formed withadditional conveyor sections 342 and right-angle elevators 300 at thecorners.

FIGS. 20A-20C depict an elevator having an upgoing path and ahorizontally offset downgoing path for an elevator carriage. An infeedconveyor section 350 feeds trays 160 to an upgoing elevator 352providing a vertical guide track 354 for elevator carriages 356. Acarriage 356 at the bottom of the upgoing guide path defined by thevertical tracks 354 with its stator rails aligned with the stator railsof the infeed conveyor section 350 receives a tray 160. Stators in thevertical guide tracks 354 energize vertical translators of two-axistranslators 358 at the corners of the carriage 356 to raise the carriageand the tray 160 sitting atop it, as shown in FIG. 20B. Once thecarriage 356 reaches the top of the upgoing guide path, horizontalstators along upper horizontal guide tracks 360 energize horizontaltranslators of the two-axis translators 358 to move the carriage 356from atop the upgoing elevator 352 to atop a downgoing elevator 362. Thedowngoing elevator has a vertical guide track defining a downgoing guidepath adjacent to the upgoing guide path. The downgoing guide path servesas a return path for emptied carriages 356. A lower horizontal guidepath 364 guides the trays back into the home position at the bottom ofthe upgoing elevator 352 in position to receive another incoming tray160. Thus, the elevator allows a number of carriages 356 to circulatearound the closed loop formed by the upgoing and downgoing guide pathsand the upper and lower horizontal guide paths. When the tray-carryingcarriage 356 is at the top of the downgoing elevator 362, as in FIG.20C, the carriage's rail stator is energized to propel the tray 160 offonto a discharge conveyor section 366. The discharge conveyor 366 can becontained within a pipe 368 suspended from above to prevent anythingfrom falling from the trays onto the floor or onto persons or conveyorsbelow and to prevent contamination of products on the conveyor trays 160from external sources.

Details of the two-axis translators 358 are shown in FIG. 31.Outward-facing pole faces 480 of a core 482 are arranged in an array.Three-phase horizontal and vertical windings 484, 485 on the core 482allow the translator 358 to move vertically or horizontally in adirection 486 parallel to the carriage rails. The carriages 356 havesafety brakes 488 suspended from the translator housings. As shown inFIGS. 32A and 32B, the safety brake 488 includes a solenoid 490 with aplunger 492 connected to an outward-facing permanent magnet 494 throughan outwardly-biasing coil spring 496. As shown in FIG. 11, the solenoid490 is electrically in series with the translator windings. As long asthe carriage 356 is powered, the solenoid 490 is actuated as shown inFIG. 32A to draw the plunger 492 and the magnet 494 inward away from theelevator guide track so that the carriage 356 can move along theelevator guide tracks. When electric power to the carriage 356 is lost,the solenoid 490 is de-actuated, and the compressed spring 496 releasesto push the plunger 492 and the magnet 494 outward to a braking positionat the outside 498 of the translator housing as in FIG. 32B. The magnet494 in the braking position is close enough to the metal of the guidetracks for magnetic attraction to hold the unpowered carriage 356 inplace and prevent it from plummeting to the bottom of the elevator.

The conveyor tray 160 in FIG. 21A can be used as a cover for a conveyortray 370 as shown in FIG. 21B. The tray 370 is generally the same as thecover tray 160, except that it has a rear wall 372 and a front wall 374upstanding from the rear edge 376 and the front edge 378 of thearticle-conveying surface 380. As shown in FIG. 21C, the underside ofthe cover tray 160 is supported atop the two walls 372, 374 of thecovered tray 370. The rear and front walls 372, 374 can be shaped asshown to fill the gap at the rear and front ends of the cover betweenthe skirts 172, 174 to completely enclose the volume between the twotrays 370, 160.

A conveyor for covering and uncovering a tray 370 with a cover tray 160is shown in FIGS. 22A-22D. In FIG. 22A, a cover tray 160 is transportedalong an upper conveyor section 380 in a first conveying direction 382toward an open end 384. A walled tray 370 to be covered advances in thesame direction 382 on a lower conveyor section 386 directly below theupper conveyor section 380. An elevator section (frame and guide tracksnot shown) including a carriage 388 bridges a space 390 between thelower conveyor section 386 and an aligned second lower conveyor section392 when the carriage is in a lower position as in FIG. 22B. Theelevator raises the carriage 388 with the tray 160 into an upperposition to receive the cover tray 160, as shown in FIG. 22C. Once thecover tray 160 is in place covering the lower walled tray 370, theelevator carriage 388 is lowered and the stator rails in the carriageand the second lower conveyor 392 are energized to propel the coveredtray downstream as in FIG. 22D.

The lower tray 370 is uncovered as shown in FIGS. 23A-23C. The coveredand covering trays 370, 160 are conveyed on the second lower conveyorsection 392 in a conveying direction 394 toward the elevator carriage388 in its lower position, as shown in FIG. 23A. The ends 396, 397 ofthe stator rails in the upper conveyor section 380 serve as stops thatprevent the cover tray 160 from advancing farther with the lower walledtray 370 as it proceeds onto the first lower conveyor section 386, asshown in FIG. 23B. Once the walled conveyor tray 370 is clear of theelevator carriage 388, the elevator raises the carriage to the upperposition, energizes the carriage's stator rails, and propels the covertray 160 onto the upper conveyor section 380 as shown in FIG. 23C.

FIGS. 24 and 25 depict a diverter section usable in conveyorsconstructed of conveyor segments as in FIG. 1. The diverter section 400comprises a circular track 402—a ring, for example—that houses a curvedstator 404 subtending an angle α around the circular track. An identicalcurved stator (not shown) is diametrically opposite the curved stator404 in the circular track 402. The circular track 402 is supported in adiverter frame 406. Two orthogonal pairs of side rails 408, 410 aresupported on translators 412 that ride on a raceway ledge 414 of thecircular track 402. One pair of the side rails 410 is optional. The siderails 408, 410 may be manually lifted from the ledge 414 for repair,replacement, or cleaning.

FIGS. 26A-26D show a diverting conveyor using the diverter section 400of FIGS. 24 and 25. The diverter section 400 resides in a gap 401 (FIG.26C) between an infeed conveyor section 416, an inline dischargeconveyor section 418, and a side-off conveyor section 420. The infeedconveyor section 416 conveys trays 160 toward the diverter section 400in a conveying direction 106. The curved stators in the circular track402 inductively energize stators in the inline rails 408 in the diverter400 to send a leading tray 160A straight across the diverter onto theinline discharge conveyor section 418, as shown in FIG. 26B. When a tray160B meant to be diverted onto the side-off discharge conveyor section420 reaches the diverter 400, the curved stators are energized to rotatetranslators over a divert angle δ until the inline diverter rails 408are aligned with the rails 422 of the side-off conveyor section 420, asshown in FIG. 26C. The curved stators in the circular track 402 thenenergize the stators in the diverter rails 408 to propel the tray 160Bonto the side-off conveyor section 420, as shown in FIG. 26D. The angleα (FIG. 25) subtended by the stationary curved diverter stator isgreater than or equal to the divert angle δ of the conveyor. As shown inFIGS. 26A and 27, the rails of the discharge conveyor sections 418, 420dip down to provide notches 424, 426 at their intersection toaccommodate the passing tray skirts.

A conveyor with a curved lower return is shown in FIG. 28. The conveyorcomprises a flat upper main carryway section 430 with a curved lowerreturnway section 432 directly below. The upper carryway 430 isconstructed of one or more conveyor segments as in FIG. 1. The lowerreturn is constructed of similar segments, but with curved rails. Andportions of the lower returnway conveyor section include two endportions 434, 436 that are coplanar with the ends of the carrywaysection 430 to resemble a gondola. The rails of the carryway section 430and the end portions 434, 436 are aligned across narrow gaps 438, 440.The gaps 438, 440 are narrow enough for trays 160 on the carrywaysection 430 to pass over with little slowdown and wide enough for traysto move onto the returnway section 432 without contacting the carrywaysection.

FIGS. 29A and 29B show a skirtless tray 450 having two orthogonal pairsof translators 452, 454 at the underside 456 of the tray. The upper side458 of the tray 450 provides a flat article-supporting surface. Thetranslators 452, 454 comprise permanent-magnet arrays whose magneticfields are directed downward perpendicular to the tray'sarticle-supporting surface 458 and underside 456. Corner magnets 459,such as Halbach arrays, are optionally disposed in the corners of thetray 450 for magnetic levitation as described subsequently. The traysmay also include side, front, and rear clamping magnets 460 at the traysides so that the trays can be used to form a larger multi-tray 462 asin FIG. 30. The clamping magnets are like those in the trays 264 shownin FIG. 16. The skirtless trays 450 with underside translators aredesigned to run on flat-top rails 466 with stators that form linearmotors with the translators 452, 454. The rails 466 with embeddedstators serve as a tray guide for the trays 450. In FIG. 30 two conveyorsections 468, 470 are arranged side by side to allow for the formationof the multi-tray 462. Connecting structure 472 maintains the left andright rails in parallel.

Another version of a conveyor segment embodying features of theinvention is shown in FIGS. 33 and 34. The conveyor segment 500 has twoparallel stators 502, 504 that extend in length from one end of thesegment to the other. The stators 502, 504 are ironless and spaced aparta distance substantially the same as the distance between oppositetranslators 452 on the trays 450 (FIG. 29B). The stators 502, 504 eachproduce a magnetic flux wave that travels along the length of the statorin a conveying direction 506.

Electrically conductive magnetic-levitation (maglev) plates 508, 510extend along the length of the conveyor segment 500 laterally outward ofthe stators 502, 504. While a conveyor tray 450 as in FIG. 29B ispropelled in the conveying direction 506 by the stators 502, 504, thetray's corner magnets 459 (FIG. 29B) induce electric currents in themaglev plates 508, 510 that generate reactive magnetic fields opposingthe corner magnets' fields with enough force to levitate the trays for alow-friction ride. Position sensors 511 are positioned along the lengthof the conveyor segment 500 to detect the presence of trays at theirpositions and send a sensor signal indicating that detection to anelectronic drive-control circuit 512. Electric power and communicationwiring to the drive control 512 can be routed to external circuits orcomputers through legs 516 of a conveyor frame 514. The stators 502,504, the position sensors 511, the electronic drive-control circuits512, and the wiring are all encapsulated in a tray-guide housing 518having a flat top surface 520 and forming a tray guide along which traysare propelled. Just inside the housing 518 at each end along both sidesare alignment magnets 522 or ferrous elements attracted by the magnetsto align adjacent sections as in FIG. 5. In the conveyor segments ofFIGS. 30 and 34, the tray guides support the trays along the tops of thetray guides by magnetic levitation rather than directly by contact as dothe tray guides in the conveyor segments of FIG. 1. Like the trays inFIG. 6, the trays 450 are easy to remove and replace withoutinterference from interlocking or other conveyor structure.

FIG. 35 shows another version of a conveyor segment in which the maglevplates 508, 510 of FIG. 33 are replaced by air ducts 524, 526.Pressurized air from an air source (not shown) is injected into theducts 524, 526 and expelled through openings 527 in the tops of theducts to levitate conveyor trays on an air cushion. In this case cornermagnets 459 as in FIG. 29B are not required on the trays 450.

The lateral alignment of abutting conveyor segments 500, 500′ is shownin FIG. 36. In this example one conveyor segment 500 has a pair ofalignment magnets 522 at one side and a pair of ferrous elements 523 atthe other side. The facing end of the adjacent conveyor section 500′ hasa pair of magnets 522 at one side and a pair of ferrous elements 523 atthe other. The magnets 522 attract the ferrous elements 523. The lateraldimensions of the magnets 522 and ferrous elements 523 match foraccurate lateral alignment of the abutting segments 500, 500′. Ofcourse, all the ferrous elements 523 may be replaced with magnets ofopposite polarity to the confronting magnets of the abutting conveyorsegment. But by arranging the magnets 522 and ferrous elements 523 asdescribed, all the segments can be made the same, and the polarity ofthe magnets will not matter.

As shown in the conveyor section 524 of FIG. 37, a cover 526 provides asmooth joint between the housings 518 of abutting conveyor segments 500.As FIG. 37 also shows, the conveyor trays 450 may be advancedindividually or together in a train.

FIGS. 38 and 39 show a conveyor arrangement for a 1-to-N switch. Asingle infeed conveyor section 530 feeds conveyor trays 450 onto an x-yconveyor segment 532 extending in length perpendicular to the infeedconveyor section 530. The x-y conveyor segment 532 has two pairs ofstators 534, 536 perpendicular to each other. The first pair of stators534 drives the trays 450 in the main conveying direction 538. The secondpair of stators 536 drives the trays 450 transverse to the mainconveying direction to one of N (three are shown) discharge conveyorsections 540. The first stators 534 form linear motors with the left andright translators in the trays, and the second stators 536 form linearmotors with the front and rear translators. Conductive plates 542flanking the pairs of stators levitate the trays 450 as they advancealong the x-y conveyor segment 532.

A merge conveyor is shown in FIG. 40 in which N (three are shown) infeedconveyor sections 544A-544C propel conveyor trays 450 in a mainconveying direction 546 to an x-y conveyor section 548. The x-y conveyorsection 548 inducts the trays 450 from the infeed sections 544A-544C andtranslates them to a single discharge conveyor section 550. The topologyof the merge conveyor is the same as that of the switch conveyor ofFIGS. 38 and 39 with the main conveying direction reversed.

A multi-level conveyor 552 for a conveyor tray 450 as in FIGS. 29A and29B is shown in FIG. 42. The layout of the conveyor as shown is the sameas that for the three-dimensional tray sorter shown in FIGS. 12A-12D.And the operation is similar. Conveyor stators along horizontal andvertical guide tracks 554, 556 propel a tray-supporting carriage 558laterally and vertically. The carriage 558, shown in more detail in FIG.41, has two-axis translators 560 in translator housings 562 at eachcorner. The housings are shaped to ride in the guide tracks 554, 556.The carriages 558 also include a pair of stators 564 embedded in thecarriage body forming a carriage tray guide with the housing. Thestators reside below a continuous top tray-guide surface 561 to inducttrays 450 into the carriage and to propel them off. Like the carriage ofFIG. 10, the carriage 558 can include weight sensors 563 at the corners(only one shown in FIG. 41). The weight sensors 563 communicate and,along with the stators 564, are powered through the translators 560,which receive power inductively from the conveyor stators along theguide tracks 554, 556. Electrically conductive strips 565, like those508, 510 in the levitating conveyor segment 500 of FIG. 33, extend alongthe carriage 558 beside the stators 564 and are used in levitating thetrays 450.

Another version of a conveyor tray is shown in FIGS. 43 and 44. The tray570, instead of supporting articles on a flat top surface, supportsarticles atop rollers 572 that extend through the thickness of the bodyof the tray. Drive stators (not shown) under left and right stationaryconveyor side walls 574, 575 coact with translators (not shown) alongthe left and right side edges 576, 577 of the tray 570 to propel it in amain conveying direction 578. Front and rear walls 580, 581 on the tray570 prevent articles from falling off the front and rear edges of thetray during starts, stops, and other accelerations. The rollers 572reside in cavities 573 that open onto the upper surface 571 and theunderside of the tray body and are freely rotatable on axles definingaxes of rotation 582 oblique to the main conveying direction 578.Elongated actuating rollers 584, supported in the conveyor frameadjacent an opening 586 in the right conveyor side wall 585, rotatefreely on axles defining axes 588 parallel to the main conveyingdirection 578. The actuating rollers 584 are arranged in line with thecolumns of tray rollers 572. As the tray 570 passes over the actuatingrollers 584, the bottoms of the tray rollers 572 rotate on their obliqueaxes 582 and push articles atop the rollers off the side of the tray 570and through the opening 586 in a right-side divert direction 590. Rollerballs without axles and rotatable in all directions could alternativelybe used in the trays and actuated by the same actuating rollers.

FIG. 44 shows the same conveyor with trays 570 having rollers 572arranged at the same oblique angle as in FIG. 43. A set of actuatingrollers 584′ is supported in the conveyor frame adjacent to an opening592 in the left side wall 574. A tray 570 traveling in the mainconveying direction 578 is stopped after passing the actuating rollers584′. The stator field is reversed to drive the tray 570 in the reversedirection 594 back over the actuating rollers 584′. The tray rollers 572engaging the actuating rollers 584′ in the reverse direction 594opposite to the main direction rotate in the opposite direction to pushconveyed articles through the opening 592 in the left side wall 574 in aleft-side divert direction 596.

The conveyor tray 600 in FIG. 45 has stacked roller sets 602 (FIG. 45A)arranged in columns. The bottom roller 604 of each set protrudes beyondthe underside of the tray 600. The top roller 606 protrudes beyond theupper surface 608 of the tray 600. The top roller 606 rests on thebottom roller 604—at least when supporting an article—so that rotationof the bottom roller in one direction causes the top roller to rotate inthe opposite direction. (The roller set in FIG. 45A is shown withoutside supports and axles for the top roller 606 for clarity.) Both thetop and bottom rollers 604, 606 are arranged to rotate on parallel axlesdefining axes 610, 611 oblique to the conveying direction 578. As theconveyor tray 600 is propelled over the actuating rollers 584, thebottom rollers 604 rotate forward on their axes 610, which rotates thearticle-supporting top rollers 606 rearward. Because the component ofrearward rotation of the top tray rollers 606 equals the forward motionof the trays 600 along the conveyor, articles are diverted off the traysin a divert direction 612 perpendicular to the main conveying direction578.

The conveyor tray 614 shown in FIGS. 46 and 46A has tray rollers 616that rotate on axles defining axes of rotation 618 parallel to the mainconveying direction 578. An array of caster-like actuating rollers 620,supported in the conveyor frame, provides tray-roller actuation in thisversion. The freely rotatable actuating rollers 620 can be swiveledabout a vertical axis 613 by a rack-and-pinion system to change theiraxes of rotation 622. With the actuating rollers 620 angled oblique tothe main conveying direction 578 as shown, the tray rollers 616 rotateto push articles across the tray 614 toward an opening 624 in the rightside wall 626. Although the tray rollers 616 push the articles off thetray at 900 relative to the tray without contacting the front and reartray walls 617, 619, they exit through the opening 624 in an obliquedirection 628 because of the motion of the tray in the conveyingdirection 578. When the actuating rollers 620 are swiveled so their axes622 are at the same oblique angle on the other side of the mainconveying direction, the actuated tray rollers 616 rotate toward theleft side wall 627 and through an opening 625 in a divert direction 629.Thus, the conveyor is useful for diverting articles off the trays ineither direction by changing the orientation of the actuating rollers620.

The passive actuating rollers 584 of FIGS. 43-45 could be replaced by atray-roller actuator in the form of a flat bearing surface on which thetray rollers 572, 604 ride. The flat bearing surface can be stationary,or it can be a moving surface, such as the outer surface of a belt. Ortray-roller rotation can be achieved magnetically orelectromagnetically. As one example, the tray-roller actuator supportedin the conveyor frame could be permanent magnets, electromagnets, orstators producing magnetic or electromagnetic fields interacting withferrous, magnetic, or electrically conductive rotors in the tray rollers572, 604, 616 of FIGS. 43-46. FIG. 55 shows a conveyor segment 100 as inFIG. 1 with a linear-motor stator 712 housed in a smooth housing betweenthe side rails 102, 104. A conveyor tray 714 has an array of rollers 716with rotors made of permanent magnets or electrically conductivematerial that form linear motors with the stator 712, which canselectively actuate the rollers 716 into rotation.

A rail scrubber 630 is shown in FIGS. 47 and 48 riding the rails 632,633 on a conveyor segment 634. The scrubber 630 is shown in this examplewith three fluid tanks: a soap tank 636, a water tank 637, and asanitizer tank 638. Each tank is in the shape of an inverted U with aspace between the legs of the inverted U. A drive system including adrive motor and battery (not shown) are housed in a housing 640 receivedin the space. The motor, powered by the battery, drives front or reardrive wheels 642, 643 or both to drive the scrubber 630 along the rails632, 633. The wheels 642, 643 are mounted on axles 644 that extendthrough the housing 640. The axles 644 are coupled to the drive motor.The wheels 642, 643 each have a central groove 646 that receives therail 632, 633 and prevents derailment. The scrubber 630 also includes atleast one set of scrubbing wheels 648, two sets in this example, toscrub both rails 632, 633. Like the drive wheels 642, the scrubbingwheels 648 are mounted on axles 650 that extend through the centralhousing 640. The scrubbing wheels 648 are also driven by the drivemotor, but perhaps geared differently to rotate at a higher speed thanthe drive wheels 642. Or the scrubber wheels 648 can be driven byseparate motors. The scrubbing wheels 648 include two wheel halvesseparated by a gap. Scrub-brush pads on confronting faces of the twowheel halves scrub the rail received in the gap. Soap, water, andsanitizer dispensers 652, 653, 654 include fittings 655 connected intothe tanks 636, 637, 638, upper and lower spray nozzles 656, 657, andtubing 658 connecting the fittings to the lower nozzles. The dispensers652, 653, 654 are on each side of the tanks 636, 637, 638 with thenozzles directing a spray at the tops and bottoms of the rails 632, 633.The housing 640 also houses a scrubber computer that controls the speedsof the drive and scrubbing wheels and other electronic and power-supplycircuits.

The rail scrubber 630 receives power inductively from the statorwindings in the rails 632, 633 through secondary coil windings housed inscrubber appendages 662, 663 that ride along the rails. A single coilmay suffice. The ac power transferred by transformer action to the coilsis converted to dc power to power the electronics and charge the batteryor drive the motors. Alternatively, the drive wheels 642 or the scrubberwheels 648 or both could include magnetic or electrically conductiverotors that are driven by the rail stators. In such a case a drive motorwould not be necessary. Or the secondary coil could be replaced by atranslator that responds to a rail-stator-generated magnetic flux wavetraveling along the rail by pushing the scrubber along the rails. Inthat case the drive rollers 642 could be idle wheels not coupled to adrive motor.

The tops and sides of the scrubber 630 of FIG. 47 are covered by asmooth stainless steel cover 660 as shown in FIG. 48. Scrapers 664extend outward from a front face 666 of the cover 660. The scrapers 664have an inverted-U cross section, a tapered top surface 668, and taperedsides 670 to remove bulk debris from the tray drive rails 632, 633,which are received in the inverted U. The scrapers 664 taper inward awayfrom the front face 666 of the cover 660.

A similar scrubber 910 for cleaning the top surface 520 of thetray-guide housing 518 of a conveyor segment 500 as in FIGS. 33 and 34is shown in FIG. 59 without a cover. This scrubber differs from thescrubber of FIG. 47 in that its wheels 912 don't ride on rails. Rather,they ride along the top surface 520 of the tray-guide housing 518.Another difference is that the scrubber wheels 914 are rotated 90° fromthe scrubber wheels 648 of FIG. 47. Brushes 916 on the bottoms of thescrubber wheels 914 scrub the top surface 520 of the tray guide. Water,soap, and sanitizer are sprayed onto the top surface 520 through spraynozzles 918. The scrubber is powered by an internal battery or by alinear motor formed by the stator in the conveyor segment andpermanent-magnet or electrically conductive rotors forming a translatorfor the scrubber 910.

In some applications, it's important that trays used to transportcertain products not be used to transport other products. This isespecially true where cross-contamination is unacceptable. One way toavoid cross-contamination by preventing trays for one product from beingused for another product is shown in FIG. 49. Four separate conveyorlines 671, 672, 673, 674 are shown. Each conveyor line is dedicated toan individual product type or family, and the trays 681, 682, 683, 684bear identification as acceptable carriers for an individual producttype or family. So each tray is an assigned member of one of a number offamilies that can be determined from the identification. Theidentification may be anything that can be detected by a sensor 676positioned at a sensing position alongside the conveyor or embeddedwithin the conveyor stator rails 678. Examples of identifiable indicia675 include tray shape, tray color, tray markings, bar codes, otherproduct codes that can be read by optical sensors or determined byvisioning systems, RFID tags readable by RFID readers, and magnetarrangements on the trays that are readable by magnetic sensors. Whenthe sensor 676 detects a tray from a family not assigned to the sensor'sconveyor, a local or system controller 679 receiving the sensor signalstops the conveyor and sounds an alarm or displays a warning so that anoperator can remove the offending tray.

Other sensors that detect process parameters, such as temperature, mayalso be used to detect valid process temperature ranges and dwell times.For example, in a tray-washing process, the tray sensor would be used tovalidate proper wash, rinse, and dry cycles. The process sensors couldbe in or on the trays themselves or positioned along the conveyor lineswhere the trays undergo the process.

Each of the conveyor lines 671-674 shown in this example comprises amain conveyor section 686 defining a carryway conveying path on whichthe trays 681, 682, 683, 684 carry products and a return conveyorsection 688 defining a return conveying path on which the trays areempty. The infeed end of the main conveyor section 686 is linked to thedischarge end of the return section 688 by an infeed diverter section690. The discharge end of the main conveyor section 686 is linked to theinfeed end of the return section 688 by a discharge diverter section692. The diverter sections 690, 692 may be the same as those shown inFIGS. 14A-14C.

The description of the operation of the fourth conveyor line 674exemplifies how each of the other conveyor lines 671-673 operates. Thetrays 684 of the family assigned to the predetermined process to becarried out along the main conveyor section 686 are fed onto the mainconveyor section from the return conveyor section 688 by the infeeddiverter 690. Only those trays 684 passing the sensor 676 that areidentified by the controller 679 as dedicated to the fourth conveyorline 674 are passed onto the main conveyor section 686. After the trays684 complete their processing on the main conveyor section 686 and theirproducts are removed, they may be diverted by the discharge diverter 692back to the return conveyor section 688 or diverted elsewhere forcleaning. Cleaned trays can be returned to the return conveyor section688. Or the cleaning process can be carried out automatically along thereturn conveyor section 688 in one or more enclosed automatic washingstations 689. In all the tray-conveyor versions described in thisapplication, fully automatic washing-station enclosures 689 can beinstalled on the return sections in one or more cleaning zones to cleanthe empty trays as a substitute for manual tray removal and cleaning. Orthe washing stations in the cleaning zones can be completely manual orsemi-automatic and require some complementary human activity. Washingstations in the return sections of the multiple-stator conveyor systemsdescribed could also be used in single-stator tray conveyors.

If it's necessary or required that the conveyor sections 686, 688, 690,692 be cleaned upon completion of a process or upon the detection of anunacceptable conveyor tray, all the trays 674 are removed andsequestered for cleaning, for example, and a scrubber 630 is placed onthe conveyor line 674 as shown in FIG. 50. The scrubber 630 runs alongall the conveyor sections 686, 688, 690, 692 to remove residue from therails 694. After the scrubber 630 has cleaned the rails 694, it isremoved from the conveyor line 674. The sequestered trays 684 can thenbe put back on the conveyor line 674, typically on the return conveyorsection 688. Cleaning of the rails can also be required whenever aninappropriate tray is detected.

Alternatively, the conveyor line 674 can be used for a different processor for the same process on different products. If contamination from theproducts or by-products of the previous process run is unacceptable, adifferent family of identifiable trays specific to the process being runis used. For example, to avoid contamination with allergens such asthose associated with peanuts, a peanut-processing run could be followedby a subsequent process run on a different food product. The local orsystem controller 679, based on the sensor signals, passes process- orproduct-specific trays of a predetermined family and locks out trays ofother families dedicated to other processes or products. In a similarway as shown in FIG. 49, the four conveyor lines 671-674 could bededicated to four different products or processes 1-4 with correspondingdesignated conveyor trays 681-684. The local or system controller, uponidentifying a tray with the sensor 676, would lock out disallowed trays.In that way contamination is avoided. For sensitive processes, such asin the chemical, biomedical, pharmaceutical, food, and electronicsindustries, different processes have to be separated by a barrier, suchas a wall 696, into different zones. The method just described appliesas well to those circumstances.

Another way to prevent cross-contamination is to make the trays so thatonly trays of a certain family are geometrically or drivably compatiblewith a conveyor. For example, conveyors for a certain process could havea rail gauge that fits only trays of a certain family. Or the statorscould be positioned in the conveyor sections so that they align onlywith the translators in the trays of a certain family.

An overhead pipe conveyor with a same-level return is shown in FIGS. 51Aand 51B. The pipe conveyor 720 comprises two elongated enclosures, orpipes 722, 724 parallel to each other at the same level and open atopposite ends. Stators (not shown) extend along a conveying surface, inthis case, the inner bottom floor 725 of the pipes 722, 724 at left andright sides 726, 728 of the floor to propel the conveyor trays 730 likethose in FIG. 7. The pipes 722, 724 may be suspended from above byattachments 732, such as cables or rods. The two pipes 722, 724 are openat a discharge end of the infeed pipe 722 and the re-entry end of thereturn pipe 724. A carriage assembly comprises a tiltable carriage 734and a guide track 736 in the form of a partial cylinder along which thecarriage translates. The carriage 734 has a pair of left and rightstator rails 738 joined through a rotor-translator 740 by a pair ofdepending arms 742 affixed to the rotor-translator. A θ-z stator 744 ispositioned along the inner side of the cylindrical guide track 736. Theθ-z stator 744 produces a magnetic flux wave that travelscircumferentially (in θ) along the guide track 736 to tilt the tray 730about a tilt axis as shown in FIG. 51B a predetermined angle θ relativeto horizontal (as in FIG. 51A) to discharge articles 746. Magnets orferrous materials in the carriage rails 738 and in the trays 730 attracteach other enough to prevent the trays from sliding off the carriagewhen it tilts. The stator 744 also propagates a magnetic flux waveaxially (in z) along the guide track 736 to translate the carriage 734from a first position in line with the infeed pipe 722 to a secondposition in line with the return pipe 724. In that way trays 730 can bereturned. So the carriage 734 translates along its tilt axis.

An over-and-under pipe conveyor is shown in FIGS. 52A-52C. In thisversion a return pipe 750 is below an incoming pipe 752. A carriageassembly has a circulating carriage 754 with two pairs of parallelstator rails 756, 758 joined by arms 760. Shaft segments 762 parallel tothe rails 756, 758 join the arms 760 to a rotor 764. An outer stator 766rotates the rotor 764 and the stator rails 756, 758 a predeterminedangle of 180° to alternately position the stator rails in line with theupper and the lower pipes 752, 754. When the carriage 754 tilts, as inFIG. 52B, articles 746 drop from the tray 730. When the carriage 754completes its 180° rotation, both sets of carriage stator rails 756, 758are aligned with the upper and lower pipes 752, 754 because the twopairs of rails are rotationally separated by 180°. The stator rails areenergized to induct trays 730 onto the upper rails 756 for the upperpipe 752 and to return trays onto the lower rails 758 for theupside-down return trip. The ceiling 759 of the pipe 754 forms theconveying surface in the upside-down return. A scraper 760 attached tothe open end of the lower return pipe 760 is positioned to scrape debrissticking to the article-supporting surface 762 of the upside-down tray730 as it's propelled along the carriage 754. The upside-down trays 730are prevented from falling off the carriage 754 by magnets and ferrouselements as with the other conveyors just described.

An endless conveyor 769 having an upper carryway and a lower returnwayis shown in FIG. 53. The upper carryway 770 has a pair of stator rails772, 774, like those in FIG. 1, propelling trays 730, like those in FIG.7. The lower returnway 776 has a pair of upside-down stator rails 778,780. Both the carryway 772 and the returnway are supported in the sameframe 782 in this example. Rotating carriages 784 in carriage assembliesat both ends of the conveyor transfer trays 730 between the carryway 770and the returnway 776 to form an endless conveying path. Each carriage784 has four pairs of parallel stator rails 786. The four right-siderails define a right-side square 788 and the four left-side rails definea left-side square 790. The squares 788, 790 are joined by a shaft 792to a motor 794. The motor rotates the carriage 784 in predetermined 90°increments so that it stops with one of the four pairs of rails 786aligned with the carryway 770 and the opposite pair of rails alignedwith the returnway 776. The stator rails 786 aligned with the carryway770 and the returnway are activated to discharge a tray 730 onto thecarryway and to induct a tray from the returnway. Attracted magnetic andferrous material in the carriage and returnway rails 786, 778, 780 andin the trays 730 prevent the upside-down or tilted trays from falling. Acarriage like the carriage 754 in FIGS. 52A-52C can be used with theconveyor of FIG. 53, and vice versa.

An endless conveyor 920 for conveyor segments 500 as in FIG. 33 andskirtless trays 450 as in FIG. 29A is shown in FIG. 60. Conveyor statorsalong four vertical guide tracks 922 form an elevator 924 at oppositeends of the conveyor 902. Each elevator raises and lowers a carriage 926to transfer a tray 450 between an upper tray carryway 928 and a lowertray returnway 929. The carriage's embedded stators induct a tray 450from the carryway or the returnway onto the carriage 926. The carriagestators are then de-energized while the elevator 924 raises or lowersthe carriage and the supported tray. Once the carriage 926 is alignedwith the carryway 928 or the returnway 929, the carriage stators arere-energized with the opposite phasing to propel the tray 450 off andonto the carryway or returnway. The elevator 924 then lowers or raisesthe carriage 926 in position to receive the next tray 450. The carriage926 is similar to the carriage 558 of FIG. 41, but using onlysingle-axis vertical translators in translator housings 930 at eachcorner. The translator housings 930 ride in the guide tracks 922. Boththe carryway 928 and the returnway 929 are constructed of one or more ofthe conveyor segments 500 providing levitating tray guides for theconveyor trays 450.

What is claimed is:
 1. A conveyor system comprising: a plurality ofconveyor sections, each conveyor section comprising: a tray guideextending in length from a rear end to a front end of the conveyorsection and in width from a left side to a right side of the conveyorsection; a left-side linear stator extending in length through the trayguide between the rear end and the front end; a right-side linear statorextending in length through the tray guide between the rear end and thefront end; wherein the left-side linear stator is closer to the leftside and the right-side linear stator is closer to the right side;wherein the tray guide of each conveyor section comprises: a left siderail extending in length in a conveying direction; a right side railextending in length in the conveying direction parallel to the left siderail; wherein the left-side linear stator is embedded in and extends inlength along the left side rail and the right-side linear stator isembedded in and extends in length along the left side rail; a pluralityof conveyor trays having translators forming linear motors with theleft-side and right-side linear stators to drive the conveyor traysalong the tray guide in the conveying direction.
 2. A conveyor system asin claim 1 comprising: one or more carriages, each including: a carriagetray guide extending in length from a rear end to a front end of thecarriage and in width from a left side to a right side of the carriage;a left-side carriage linear stator extending in length through thecarriage tray guide between the rear end and the front end of thecarriage tray guide; a right-side carriage linear stator extending inlength through the carriage tray guide between the rear end and thefront end of the carriage tray guide; wherein the left-side carriagelinear stator is closer to the left side and the right-side carriagelinear stator is closer to the right side of the carriage tray guide; arear translator at the rear end of the carriage; a front translator atthe front end of the carriage; a pair of parallel guide tracks extendingperpendicular to the conveying direction, each of the guide tracksforming a guide path perpendicular to the conveying direction for thefront and rear translators of the one or more carriages and including alinear stator to translate the one or more carriages along the guidepath; wherein the conveyor sections are horizontally or verticallyoffset from each other across spaces; and wherein the pair of parallelguide tracks are disposed in the spaces between offset conveyor sectionsto guide the carriages along the guide path from alignment with one ofthe conveyor sections to one or more other of the conveyor sections. 3.A conveyor system as in claim 2 comprising a pair of horizontal paralleltracks forming a horizontal guide path and a pair of vertical paralleltracks forming a vertical guide path and wherein the front and the reartranslator of each of the one or more carriages each include a verticaltranslator and a horizontal translator guiding the carriage along thevertical or horizontal track.
 4. A conveyor system as in claim 2 whereinthe plurality of conveyor sections are arranged vertically offset fromeach other in a stack and wherein the plurality of conveyor sectionshave a pair of parallel vertical tracks for a carriage at an end of thestack of conveyor sections to lift and lower the carriage from oneconveyor section to another conveyor section in the stack.
 5. A conveyorsystem as in claim 2 wherein the plurality of conveyor sections arearranged with an infeed conveyor section and a plurality of dischargeconveyor sections spaced apart across a space and wherein the pluralityof conveyor sections have a pair of parallel horizontal tracks in thespace for a carriage to translate between alignment with the infeedconveyor section and each of the discharge conveyor sections.
 6. Aconveyor system as in claim 2 wherein the plurality of conveyor sectionsare arranged with a plurality of parallel infeed conveyor sections and asingle discharge conveyor section spaced apart across a space andwherein the plurality of conveyor sections have a pair of parallelhorizontal tracks in the space for a carriage to translate betweenalignment with the infeed conveyor sections and the discharge conveyorsection.
 7. A conveyor system as in claim 2 wherein the plurality ofconveyor sections are arranged with a pair of side-by-side infeedconveyor sections and a plurality of parallel discharge conveyorsections spaced apart from the infeed conveyor sections across a spaceand wherein the plurality of conveyor sections have a pair of parallelhorizontal tracks in the space for a carriage to translate betweenalignment with the infeed conveyor sections and the discharge conveyorsections.
 8. A conveyor system as in claim 1 further comprising: anelevator that includes a vertical linear stator and a vertical guidetrack; and a carriage for a conveyor tray including: a carriage trayguide extending in length from a rear end to a front end of the carriageand in width from a left side to a right side of the carriage; aleft-side carriage linear stator extending in length through thecarriage tray guide between the rear end and the front end of thecarriage tray guide; a right-side carriage linear stator extending inlength through the carriage tray guide between the rear end and thefront end of the carriage tray guide; wherein the left-side carriagelinear stator is closer to the left side and the right-side carriagelinear stator is closer to the right side of the carriage tray guide; arear translator at the rear end of the carriage; a front translator atthe front end of the carriage; wherein the vertical linear stator formsa linear motor with the front and rear translators to move the carriagesupporting one of the conveyor trays along the vertical guide trackbetween a lower position in which the top of the carriage guide is belowthe top of the tray guide of the conveyor section and an upper positionin which the top of the carriage guide is above the top of the trayguide of the conveyor section.
 9. A conveyor system as in claim 8wherein the conveyor trays further include second translators forminglinear motors with the left-side and right-side carriage linear statorsto drive the conveyor trays perpendicular to the conveying direction.10. A conveyor system as in claim 1 wherein the conveyor sections arehorizontally or vertically offset from each other.
 11. A conveyor systemas in claim 10 comprising a plurality of elevator sections, wherein theplurality of conveyor sections are arranged to form a four-sidedrectangular spiral of consecutive conveyor sections vertically offsetfrom each other wherein one of the elevator sections and one of thecarriages is disposed at each corner of the rectangular spiral to raiseand lower the carriage from one conveyor section to the next consecutiveconveyor section.
 12. A conveyor system as in claim 1 comprising: acarriage including: a carriage tray guide extending in length from arear end to a front end of the carriage and in width from a left side toa right side of the carriage; a left-side carriage linear statorextending in length through the carriage tray guide between the rear endand the front end of the carriage tray guide; a right-side carriagelinear stator extending in length through the carriage tray guidebetween the rear end and the front end of the carriage tray guide;wherein the left-side carriage linear stator is closer to the left sideand the right-side carriage linear stator is closer to the right side ofthe carriage tray guide; a rear translator at the rear end of thecarriage; a front translator at the front end of the carriage; a firstlower conveyor section having an end at a lower level; a second lowerconveyor section aligned with and having an end spaced apart from theend of the first lower conveyor section across a space at the lowerlevel; an upper conveyor section parallel to and above the first lowerconveyor section at an upper level and terminating at an end directlyabove the end of the first lower conveyor section; an elevator disposedin the space between the first and second lower conveyor sections andincluding a vertical linear stator and a vertical guide track for movingthe carriage between a lower position in which the carriage tray isaligned with the first and second lower conveyor sections and an upperposition in which the carriage tray is aligned with the upper conveyorsection; wherein the lower conveyor trays on the first lower conveyorsection have upstanding walls to support the upper conveyor traystransferred off the end of the upper conveyor section and onto the lowerconveyor trays as they pass from the first lower conveyor section to thesecond lower conveyor section with the carriage in the lower position sothat the upper conveyor trays serve as covers for the lower conveyortrays.
 13. A conveyor system as in claim 12 wherein the upper conveyortrays serving as covers for the lower conveyor trays passing over thecarriage in the lower position from the second lower conveyor section tothe first lower conveyor section are restrained by the end of the upperconveyor section, stripped from the advancing lower conveyor tray toland on the carriage, and transferred off the carriage and onto theupper conveyor section when the carriage is moved to the upper positionafter the lower conveyor trays have cleared the carriage.
 14. A conveyorsystem as in claim 12 wherein the plurality of conveyor sections arearranged with at least one infeed conveyor section and a plurality ofparallel accumulator conveyor sections arranged in multiple horizontallyoffset rows of vertically stacked conveyor sections spaced apart fromthe at least one infeed conveyor section across a space and wherein theplurality of conveyor sections have at least one pair of parallelhorizontal tracks in the space for at least one carriage to translatebetween alignment with the at least one infeed conveyor section and theaccumulator conveyor sections.
 15. A conveyor system as in claim 1comprising: a first conveyor section extending in length from a firstend to a second end; a second conveyor section extending in length froma first end to a second end and including: a first end portion at thefirst end aligned with the first end of the first conveyor sectionacross a first gap; a second end portion at the second end aligned withthe second end of the first conveyor section across a second gap; and acurved intermediate portion disposed directly below the first conveyorsection and connected between the first and second end portions.
 16. Aconveyor system as in claim 1 comprising: a first conveyor sectionextending in length from a first end to a second end; a second conveyorsection extending in length from a first end to a second end along adivert angle oblique to the length of the first conveyor section,wherein the second end of the first conveyor section is spaced apartacross a gap from the first end of the second conveyor section; a thirdconveyor section extending in length from a first end to a second endand aligned with the first conveyor section across the gap; wherein eachof the first, second, and third conveyors has a left-side rail extendingin length along the left side in a conveying direction and a right-siderail extending in length along the right side in a conveying direction;a diverter disposed in the gap and including: a circular track; a firstrail assembly including: a first rail extending in length along a firstside of the diverter; a first linear stator embedded in and extending inlength along the first rail; a first translator attached to the firstrail and electrically connected to the first linear stator; a secondrail assembly including: a second rail extending in length along asecond side of the diverter opposite to the first side; a second linearstator embedded in and extending in length along the second rail; asecond translator attached to the second rail and electrically connectedto the second linear translator; wherein the first and second railassemblies ride in the circular track; first and second stationarycurved stators at diametrically opposite positions across the diverterinterior to the circular track, each of the curved stators subtending anangle greater than or equal to the divert angle; wherein the first andsecond curved stators are activated to energize the first and secondtranslators to move the rail assemblies along the circular track betweena first position in which the first rail and the second rail are alignedwith the left-side rail and the right-side rail of the first conveyorsection and of the third conveyor section and a second position in whichthe first rail and the second rail are aligned with the left-side railand the right-side rail of the second conveyor section.
 17. A conveyorsystem as in claim 1 comprising: one or more carriages, each including:a carriage tray guide extending in length from a rear end to a front endof the carriage and in width from a left side to a right side of thecarriage; a left-side carriage linear stator extending in length throughthe carriage tray guide between the rear end and the front end of thecarriage tray guide; a right-side carriage linear stator extending inlength through the carriage tray guide between the rear end and thefront end of the carriage tray guide; wherein the left-side carriagelinear stator is closer to the left side and the right-side carriagelinear stator is closer to the right side of the carriage tray guide; arear translator at the rear end of the carriage; a front translator atthe front end of the carriage; a pair of parallel guide tracks extendingperpendicular to the conveying direction, each of the guide tracksforming a guide path perpendicular to the conveying direction for thefront and rear translators of the one or more carriages and including alinear stator to translate the one or more carriages along the guidepath; wherein the conveyor sections are horizontally or verticallyoffset from each other across spaces; and wherein the pair of parallelguide tracks are disposed in the spaces between offset conveyor sectionsto guide the carriages along the guide path from alignment with one ofthe conveyor sections to one or more other of the conveyor sections. 18.A conveyor system as in claim 1 wherein the plurality of conveyorsections are arranged to form a carryway path along which the trays cancarry articles and a return path along which empty trays return to thecarryway path and wherein the conveyor system comprises one or morecleaning zones along the return path for cleaning the trays.
 19. Aconveyor system as in claim 18 wherein at least one of the one or morecleaning zones includes an automatic washing enclosure in which thetrays are cleaned.
 20. A conveyor system as in claim 1 wherein theplurality of conveyor sections are arranged to form an endless racetrackin which at least some of the conveyor sections are curved conveyorsections.
 21. A conveyor system as in claim 1 wherein at least some ofthe conveyor sections are tilted to allow conveyed products to slide offthe trays.
 22. A conveyor system as in claim 1 wherein the conveyortrays include: a tray body having an upper surface and an oppositeunderside; a plurality of rollers in the tray body; and wherein theconveyor system includes a tray-roller actuator in one of the conveyorsections coacting with the plurality of rollers to rotate the rollers asthey pass by.
 23. A conveyor system as in claim 22 wherein the pluralityof rollers extend past the underside of the tray body and wherein thetray-roller actuator includes a plurality of actuating rollers engagingthe rollers in the tray body as the tray passes by to rotate the rollersin the tray body.
 24. A conveyor system as in claim 22 wherein theplurality of rollers extend past the underside of the tray body andwherein the tray-roller actuator includes a flat bearing surfaceengaging the rollers in the tray body as the tray passes by to rotatethe rollers in the tray body.
 25. A conveyor system as in claim 22wherein the plurality of rollers include rotors made of magnet orelectrically conductive material and wherein the tray-roller actuatorincludes a linear stator that forms a linear motor with the rotors asthe tray passes by to rotate the rollers in the tray body.
 26. Aconveyor system as in claim 22 wherein each of the rollers comprises abottom roller extending past the underside and a top roller contactingthe bottom roller and extending past the upper surface so that rotationof the bottom roller in one direction causes the top roller to rotate inthe opposite direction.
 27. A conveyor system as in claim 1 wherein theconveyor trays have identifying indicia and wherein the conveyor systemfurther comprises sensors embedded in the tray guide to sense theidentifying indicia.
 28. A conveyor system as in claim 27 furthercomprising a controller and wherein the sensors provide signalsindicating the positions of the conveyor trays and their identifyingindicia to the controller and wherein the controller sends controlsignals to energize the left-side and right-side linear stators tocontrol the motion of the conveyor trays.
 29. A conveyor system as inclaim 27 further comprising a controller and wherein the indiciaindicate a family of which the tray is a member, the sensor senses theindicia and sends a sensor signal to the controller, the conveyorsection is assigned to convey trays that belong to a predeterminedfamily, and the controller determines the family of the tray from thesensor signal and stops the conveyance of the tray on the conveyor ifthe family of the tray does not match the predetermined family of theconveyor section.
 30. A conveyor system as in claim 1 further comprisinga scrubber that rides along the tray guide to clean the plurality ofconveyor sections.
 31. A conveyor system as in claim 1 wherein theconveyor trays are made of an electrically conductive material formingthe translators, which form linear induction motors with the left-sideand right-side linear stators.
 32. A conveyor system as in claim 1wherein the translators each comprise a left translator proximate theleft-side linear stator and a right translator proximate the right-sidelinear stator.
 33. A conveyor system as in claim 1 comprising a conveyorframe and stator drive electronics and wires enclosed in the conveyorframe, wherein the wires connect the stator drive electronics to atleast one of the left-side and right-side linear stators.
 34. A conveyorsystem as in claim 1 further comprising sensors embedded in the trayguide at sensing positions to detect the presence of a conveyor tray atthe sensing positions.
 35. A conveyor system as in claim 1 furthercomprising magnets embedded at the ends of the tray guide of a conveyorsection and attracted to the magnets at the ends of the tray guide of anadjacent conveyor section to align with the tray guides of the adjacentconveyor sections.
 36. A conveyor system as in claim 1 furthercomprising at least one magnet embedded at first ends of the tray guideof a conveyor section and ferrous elements at opposite second ends ofthe tray guide, wherein the ferrous elements are attracted to themagnets at first ends of the tray guide of an adjacent conveyor sectionto align with the tray guide of the adjacent conveyor sections.
 37. Aconveyor system as in claim 1 further comprising a source of pressurizedair and wherein the tray guide includes left and right airflow networksalong the left and right sides respectively pressurized by the source ofpressurized air and a main tunnel extending along the length of the trayguide and spur tunnels branching off the main tunnel to openings ontothe top of the tray guide to provide an air bearing for the conveyortrays.
 38. A conveyor system as in claim 1 wherein the left- andright-side linear stators are ironless stators.
 39. A conveyor system asin claim 1 further comprising a left electrically conductive strip alongthe left side of the tray guide and a right electrically conductivestrip along the right side.
 40. A conveyor system comprising: aplurality of conveyor sections, each conveyor section comprising: a trayguide extending in length from a rear end to a front end of the conveyorsection and in width from a left side to a right side of the conveyorsection; a left-side linear stator extending in length through the trayguide between the rear end and the front end; a right-side linear statorextending in length through the tray guide between the rear end and thefront end; wherein the left-side linear stator is closer to the leftside and the right-side linear stator is closer to the right side; aplurality of conveyor trays having translators forming linear motorswith the left-side and right-side linear stators to drive the conveyortrays along the tray guide in the conveying direction; an elevator thatincludes a first vertical linear stator and a first vertical guide trackdefining an upgoing guide path and a second vertical linear stator and asecond vertical guide track defining a downgoing guide path adjacent theupgoing guide path; a carriage including: a carriage tray guideextending in length from a rear end to a front end of the carriage andin width from a left side to a right side of the carriage; a left-sidecarriage linear stator extending in length through the carriage trayguide between the rear end and the front end of the carriage tray guide;a right-side carriage linear stator extending in length through thecarriage tray guide between the rear end and the front end of thecarriage tray guide; wherein the left-side carriage linear stator iscloser to the left side and the right-side carriage linear stator iscloser to the right side of the carriage tray guide; a rear translatorat the rear end of the carriage; a front translator at the front end ofthe carriage; wherein the first vertical linear stator forms a linearmotor with the front and rear translators to move the carriage upwardalong the first vertical guide track from a lower level to an upperlevel and wherein the second vertical linear stator forms a linear motorwith the front and rear translators to move the carriage downward alongthe second vertical guide track from the upper level to the lower level.41. A conveyor system as in claim 40 wherein the elevator furthercomprises: a magnetic brake connected to receive electrical power fromone of the front or rear translators and being operable in a brakingposition to attract metal in the first and second vertical guide trackswhen one of the front or rear translators is powered.
 42. A conveyorsystem as in claim 40 wherein the elevator comprises: a first horizontallinear stator and a first horizontal guide track at the upper leveldefining an upper guide path extending from the upgoing guide path tothe downgoing guide path; and a second horizontal linear stator and asecond horizontal guide track at the lower level defining a lower guidepath extending from the downgoing guide path to the upgoing guide path.43. A conveyor system as in claim 40 further comprising: a conveyorsection abutting the elevator at the upper level to receive the conveyortrays from the carriage on the first horizontal guide track; and a pipedisposed at the upper level through which the conveyor section extends.44. A conveyor system comprising: a conveyor comprising a singleconveyor segment or a series of conveyor segments, each conveyor segmentcomprising: a tray guide extending in length from a rear end to a frontend of the conveyor segment and in width from a left side to a rightside of the conveyor segment; a left-side linear stator extending inlength through the tray guide between the rear end and the front end; aright-side linear stator extending in length through the tray guidebetween the rear end and the front end; wherein the left-side linearstator is closer to the left side and the right-side linear stator iscloser to the right side; wherein the tray guide of each conveyorsection comprises: a left side rail extending in length in a conveyingdirection; a right side rail extending in length in the conveyingdirection parallel to the left side rail; wherein the left-side linearstator is embedded in and extends in length along the left side rail andthe right-side linear stator is embedded in and extends in length alongthe left side rail; a plurality of conveyor trays driven along the trayguide, each of the conveyor trays having a translator forming a linearmotor with the left-side and right-side linear stators to drive theconveyor trays in the conveying direction.
 45. A conveyor systemcomprising: a plurality of conveyor sections, each conveyor sectioncomprising: a tray guide extending in length from a rear end to a frontend of the conveyor section and in width from a left side to a rightside of the conveyor section; a left-side linear stator extending inlength through the tray guide between the rear end and the front end; aright-side linear stator extending in length through the tray guidebetween the rear end and the front end; wherein the left-side linearstator is closer to the left side and the right-side linear stator iscloser to the right side; a plurality of conveyor trays havingtranslators forming linear motors with the left-side and right-sidelinear stators to drive the conveyor trays along the tray guide in theconveying direction; a carriage having a carriage tray guide and acarriage support frame at an end of the conveyor supporting the carriagetray guide in alignment with the tray guide on the conveyor in a firstposition to receive a conveyor tray from the conveyor, wherein thecarriage support frame includes a stator and wherein the carriageincludes a translator forming a linear motor with the stator energizableto move the carriage with the conveyor tray to a second position inalignment with another conveyor and back to the first position.
 46. Aconveyor system as in claim 45 wherein the tray guide comprises a leftside rail along the left side and a right side rail along the rightside.
 47. A conveyor system as in claim 45 wherein the carriage includesa left linear stator embedded in the carriage tray guide along the leftside and a right linear stator embedded in the carriage tray guide alongthe right side to move the conveyor trays along the carriage.
 48. Aconveyor system as in claim 45 wherein the carriage includes a housingat each end of the carriage tray guide and a translator embedded in eachhousing and wherein the carriage support frame includes a pair of tracksextending perpendicular to the conveying direction of the conveyor, eachof the tracks receiving the housings at one of the ends of the carriagetray guide and including a stator forming a linear motor with each ofthe translators whose housings are received in the track to drive thecarriage along the tracks.
 49. A conveyor system as in claim 45 whereinthe carriage includes vertical translators and horizontal translatorsand wherein the carriage support frame includes vertical tracks withembedded vertical stators forming vertical linear motors with thevertical translators to translate the carriage vertically along thevertical tracks and wherein the support frame includes horizontal trackswith embedded horizontal stators forming horizontal linear motors withthe horizontal translators to translate the carriage horizontally alongthe horizontal tracks.